Sailboards such as are exemplified in the U.S. Pat. No. 3,487,800 have become a very popular recreational item. In essence, the sailboard consists of a unit such as a surfboard or the like that has some means provided for lateral stability and to which a sail has been provided on a mast that is connected to the board by means of a universal joint.
One of the great enjoyments of a sailboard is the speed that is attained. For example, it is not uncommon with a wind velocity in the vicinity of 20 knots for the vehicle to attain speeds in the vicinity of 12 to 14 knots. If additional speed is desired, one of the solutions is to reduce the wetted surface.
Hydrofoils have been proven effective on vessels that are propelled by motors since the motor provides a strong and controllable thrust. The same is not true on sailboats where the power source which is wind is more variable. When hydrofoils have been used on sailboats they have been employed in the bow and the stern consisting of athwartships foils supported by struts below the hull, see for example the Steinberg U.S. Pat. No. 3,373,710. This arrangement works well with engine power but the excessive underwater drag of the struts and the foils proves too much for sail power to overcome, particularly in light winds. In addition the variable nature of the wind power often leads to a condition known as "porpoising" where the lead foil loses lift suddenly causing the bow to plunge and rise erratically.
Hydrofoils have been successful on large power passenger and military boats, but their use requires large engines and skilled operation.
Ski structures have been used on power recreational watercraft, as for example, as seen in U.S. Pat. No. 2,817,101. In this form they do not have complete stability and are subject to "porpoising and pounding" in rough seas.